1. Field of the Invention
This invention relates to a system for analysis of molten metal. More particularly, this invention relates to a system capable of removing a solid sample from a source of molten metal; dissolving the sample; and then analyzing the dissolved sample.
2. Description of the Prior Art
In the production of metal alloys such as, for example, an aluminum base alloy, it is desirable to determine the alloy content while the alloy is still in molten form. This, in turn, permits the addition of further alloying materials, or more base metal if the alloying metals are more concentrated than desired, while the alloy mixture is still molten.
Various methods of analyzing such molten metals are possible. In its simplest form, such analysis could comprise taking a sample from the melt and sending it out for spectral analysis. This, of course, would involve an unacceptable time lag. On the other hand, however, direct spectral analysis of the molten metal would create problems if sensitive spectrometer equipment was located in immediate proximity to a furnace containing molten metal.
Various alternative methods of analysis have been previously proposed. For example, Bojic U.S. Pat. No. 3,659,944 describes a system wherein a stream of molten metal is drawn into a spark chamber where the molten metal comes in contact with one electrode. The light or radiation generated by a spark between the molten metal and a second electrode is directed into a spectrometer to provide direct analysis of the molten metal. However, such a method involves the transport of molten metal from a furnace to the spark chamber and further results in the need to transmit the emitted spectra to the spectrometer if the spark chamber is located near the molten metal.
Virgolet U.S. Pat. No. 3,669,546 illustrates a system for analysis of molten metal wherein one electrode is placed directly into the molten metal bath and an electric arc is generated between the surface of the bath and another electrode placed adjacent the surface. The light emitted from this electric arc is then transmitted by a series of mirrors to a spectrograph where the light is analyzed to determine the content of the molten metal. Similar systems are disclosed in Bojic et al U.S. Pat. Nos. 3,645,628 and 3,672,774 wherein light is produced by generating sparks between an electrode and the surface of a crucible filled with molten metal and in contact with a second electrode. The light thus produced is directed to a spectrometer for analysis. Such systems, however, require the transmission of the emitted light to a spectral analysis apparatus spaced some distance from the furnace and thus some distance from the point of generation of the light.
British Patent Specification No. 1,116,052 shows a mechanism for analyzing molten material by passing a gas under pressure into the molten metal to produce metal particles which are then transported out of the bath to a spectrograph for analysis by feeding the particles or dust into a plasma jet. Production of metal particles from molten metal is also shown by Maringer U.S. Pat. No. 4,154,284 who teaches the production of metal particles such as metal flake by dipping a portion of a rotating wheel into a pool of molten metal. The wheel is provided with sawtooth-like serrations which pick up the molten metal as the wheel passes through the molten metal pool. As the wheel emerges from the molten metal, centrifugal force and/or contact with gases cause the now solidified metal to break off as flakes from the rotating wheel. The serrated surface of the wheel may also be cleared of any adhering metal from the molten metal pool by contacting the serrations with a brush.
Kenney International Application PCT/US84/01148, however, points out that problems such as interruption of particle flow due to clogging can occur in attempting to transport such metal powder. Instead, Kenney proposes a system for analysis of molten metal wherein an atomization die is used in connection with pressurized inert gas to form an aerosol or dispersion of solidified metal particles in the gas. This aerosol or dispersion is then delivered to an inductively coupled plasma torch which causes the particles to emit spectra characteristics of their constituent elements which may then be analyzed with a spectrometer.